An automatic welding apparatus which relatively moves a base metal and a welding wire is comprised of a welding machine and a controller which controls the movement of a welding torch for holding the welding wire.
With such an automatic welding apparatus, it is necessary to move to an ensuing operation after confirming that the welding wire and the base metal have not been fused together upon completion of welding.
If the welding torch is moved with the welding wire remaining fused, an excessively large force is applied to the welding torch, which will deform the welding torch, so that the detection of the fusion of the welding wire is an essential requirement in automatic welding.
Referring to FIG. 3, a description will be given of a conventional technique of detecting the fusion of the welding wire.
In FIG. 3, reference numeral 11 denotes a welding machine; 12, a welding wire feed motor; 13, welding wire; 17, a controller; 19, a resistor; and 18, a base metal.
At a position of welding completion, the controller 17 commands welding completion to the welding machine 11. To complete welding, the welding machine 11 first stops the wire feed motor 12, but continues to output a specific welding output, and stops the welding output to the welding wire 13 after the wire feeding by the inertia of the motor has stopped.
This processing of the welding machine is for preventing fusion between the welding wire 13 and the base metal 18, and is generally referred to as wire fusion prevention processing.
By assuming that the welding machine 11 has stopped the welding output in a fixed period of time after commanding welding completion, the controller 17 applies a voltage between the welding machine 13 and the base metal 18 through a resistor 19.
If the welding machine 13 and the base metal 18 have not fused together, the voltage applied from the controller is detected as it is between the welding machine 13 and the base metal 18.
On the other hand, if the welding machine 13 and the base metal 18 have fused together, the voltage applied from the controller 17 is applied to the resistor inserted in series, and the voltage is not detected between the welding machine 13 and the base metal 18.
The controller 17 is able to confirm the presence or absence of the fusion of the welding wire on the basis of this voltage between the welding machine 13 and the base metal 18. After confirming that they have not been fused together, the operation conventionally proceeds to an ensuing operation.
In addition, a conventional arc welding process is known wherein processing is executed in a case where the wire fusion has been detected, the fusion is removed by reapplying a welding voltage between the base metal and the welding wire, and the fusion is removed by effecting the feeding of the welding wire at a low speed, stopping the feeding of the welding wire after the lapse of a predetermined time, shutting of welding voltage, or by applying the welding voltage, and wherein the number of times of execution of this processing is counted, and the fusion removal operation is executed only a predetermined number of times (e.g., refer to patent document 1).
Patent document 1: JP-B-03-069623